Fatal Neisseria (Branhamella) catarrhalis pneumonia in an immunodeficient host

A 64-year-old man with far-advanced IgA multiple myeloma presented with fulminant and rapidly fatal bronchopneumonia. Gram stains of expectorated sputum and of transtracheal aspirate revealed gram-negative intracellular and extracellular diplococci. Cultures of these specimens yielded Neisseria catarrhalis. Subsequent histologic examination of the lung confirmed the presence of numerous gram-negative diplococci in the alveolar spaces. The pathogenic potential of this nasopharyngeal commensal is discussed in both the normal and the immunosuppressed host.